Iminopyridine Ni(II) Catalysts Affording Oily Hyperbranched Ethylene Oligomers and/or Crystalline Polyethylenes Depending on the Reaction Conditions: Possible Role of In Situ Catalyst Structure Modifications

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics elastomers hyperbranched amorphous waxes and oils. In addition Brookhart’s α-diimine catalysts, iminopyridine Ni(II) complexes are among the most investigated systems. We report that bearing aryliminopyridine ligands bulky substituents both at imino moiety 6-position pyridine afford either low molecular weight polyethylene oils or prevailingly linear crystalline polyethylenes both, depending on ligand structure reaction conditions. The formation multiple active species situ is suggested by analysis post-polymerization catalyst residues, showing partial reduction function. Some related arylaminopyridine were also synthesized tested, peculiar behavior, i.e., number branches produced increases while pressure increases.